The present invention relates to programmable or electronically controllable air bearing sliders. Air bearing sliders are primarily used as mounting platforms for read/write heads in, for example, hard disk drives. In such environments it is necessary to carefully control the height of the read/write head. That is, it is necessary to control the distance between the read/write head and the disk surface to optimize the read/write characteristics.
Increased recording densities result in the necessity of designing read/write heads which fly extremely close to the recording surface. In order to move the read/write heads closer to the disk, it is generally necessary for the sliders themselves to fly closer to the disks. Unfortunately, the slider fly height is limited by head-disk interactions which increases as the slider gets closer to the disk. As the number of head disk interactions increase, the reliability of the system decreaes. Head disk interactions may be caused by, for example, debris on the disk or slider or by disk asperities.
Therefore, it would be advantageous to design a slider which reduces the number of head-disk interactions. Reducing the number of head-disk interactions may be accomplished by, for example, designing a programmable slider which flies low during a read or write operation and returns to a safe height between read/write operations. A disk drive generally includes a number of read/write heads, each mounted on a separate slider. A specific head (and thus slider) is normally used for reading or writing less than 1 percent of the time. Thus, programmable designs provide a substantial increase in reliability when compared to designs wherein the read/write head flies low all the time.
Air bearing sliders have been designed to adjust the fly height of the read/write head using a number of methods. For example, the read/write head may be mounted to the slider using a piezoelectric coupling which lowers the head independent of the slider. In other air bearing sliders, the fly height is controlled through the use of piezoelectric elements in the slider structure to change the curvature of the air bearing surface, increasing or reducing the fly height.
In those sliders wherein the fly height is programmable, a figure of merit is the relative change in fly height per unit slider deflection. This figure of merit may be expressed in microns of fly height per microradians of deflection. In this type of slider, it is desirable to achieve a maximum change in fly height per unit slider deflection. By increasing the change in fly height per unit deflection, the sensitivity of the programmable slider is increased. In addition, the voltage variation required to adjust the slider fly height is minimized.
U.S. Pat. No. 3,732,552 is directed to a magnetic head system operable in a fluid medium (e.g. air). The magnetic head is supported on a support member which uses a biasing element to hold the support member the desired distance from the record carrier (e.g. a hard disk). The fly height is varied by using the changes in the curvature of the support surface. In particular, a piezoelectric insert is used to vary the curvature of the support surface in accordance with an electric signal. This arrangement includes a center air bearing surface.
U.S. Pat. No. 3,678,482 is directed to a recording head mounted on an air bearing slider wherein the faces of the air bearing slider are designed to improve the attitude of the slider. A narrow slot is included in the air bearing slider as a means of providing hydrodynamic separation between the trailing edge of the main face and the leading edge of the satellite edge.
U.S. Pat. No. 4,555,739 is directed to a self loading air bearing slider assembly including a cross rail from which side rails and a middle rail extend. The surfaces between the middle rail and the side rails are intended to provide a sub ambient pressure region. When the slider is in flight, the repelling action of the air bearing surfaces surrounding the subambient region and attracting action of the subambient pressure region supplement the stabilizing force of the load arm. Both the middle and side rails extend the entire length of the slider.
U.S. Pat. No. 4,605,977 illustrates a slider including a plurality of rails extending longitudinally which provide the air bearing surface and a channel parallel to the motion of the data track. A flexible beam is affixed to the leading edge of the channel, providing a cantilever structure. The magnetic head is mounted on the free end of the cantilever structure. A pair of oppositely polarized piezoelectric crystals are mounted on the cantilever assembly. Thus when energized by an electrical source the cantilever beam is flexed upwards or downwards, thereby changing the distance between the magnetic head and the disk.
U.S. Pat. No. 3,863,124 describes a spacing control apparatus for maintaining the spacing between a signal transducer and a magnetic recording surface. Spacing between the signal transducer and the magnetic surfaces is maintained using electrical control signals to drive the spacing control device and thereby cause deformation of its surfaces. The elements of the spacing control apparatus are comprised of a deformable material such as a piezoelectric material. Thus, when the control signal becomes more negative, one element bends upward away from the gas flow while a second element bends downward towards the gas flow layer. This deformation causes the signal transducer to rise. When an opposite polarity signal is applied, causing the first element to bend downward into the gas flow layer and the second element to bend upward away from the gas flow, the signal transducer falls.
Other types of sliders include constant fly height air bearing slider sliders such as the Winchester or Coronado slider, which are not programmable. In the Winchester and Coronado slider two rails run the length of the slider and include tapered front air bearing surfaces. In the Winchester slider a third rail runs down the center of the slider between the two air bearing rails. A pair of non air bearing surfaces separate the center rail from the air bearing rail. In this arrangement, the read/write head is attached to the rear of the slider. A further improvement of this design is found in the Coronado slider, wherein the side air bearing rails include a pair of read/write heads, and the center rail is eliminated.
The present invention is intended to overcome the problems encountered in the prior art by electronically adjusting the relative angle of attack of the first, and second air bearing surfaces.